Message ID | 20210115181819.34732-7-ebiggers@kernel.org (mailing list archive) |
---|---|
State | New, archived |
Headers | show |
Series | fs-verity: add an ioctl to read verity metadata | expand |
On 01/15, Eric Biggers wrote: > From: Eric Biggers <ebiggers@google.com> > > Add support for FS_VERITY_METADATA_TYPE_SIGNATURE to > FS_IOC_READ_VERITY_METADATA. This allows a userspace server program to > retrieve the built-in signature (if present) of a verity file for > serving to a client which implements fs-verity compatible verification. > See the patch which introduced FS_IOC_READ_VERITY_METADATA for more > details. > > The ability for userspace to read the built-in signatures is also useful > because it allows a system that is using the in-kernel signature > verification to migrate to userspace signature verification. > > This has been tested using a new xfstest which calls this ioctl via a > new subcommand for the 'fsverity' program from fsverity-utils. > > Signed-off-by: Eric Biggers <ebiggers@google.com> Reviewed-by: Jaegeuk Kim <jaegeuk@kernel.org> > --- > Documentation/filesystems/fsverity.rst | 9 +++++++- > fs/verity/read_metadata.c | 30 ++++++++++++++++++++++++++ > include/uapi/linux/fsverity.h | 1 + > 3 files changed, 39 insertions(+), 1 deletion(-) > > diff --git a/Documentation/filesystems/fsverity.rst b/Documentation/filesystems/fsverity.rst > index 6dc5772037ef9..1d831e3cbcb33 100644 > --- a/Documentation/filesystems/fsverity.rst > +++ b/Documentation/filesystems/fsverity.rst > @@ -236,6 +236,7 @@ This ioctl takes in a pointer to the following structure:: > > #define FS_VERITY_METADATA_TYPE_MERKLE_TREE 1 > #define FS_VERITY_METADATA_TYPE_DESCRIPTOR 2 > + #define FS_VERITY_METADATA_TYPE_SIGNATURE 3 > > struct fsverity_read_metadata_arg { > __u64 metadata_type; > @@ -256,6 +257,10 @@ This ioctl takes in a pointer to the following structure:: > - ``FS_VERITY_METADATA_TYPE_DESCRIPTOR`` reads the fs-verity > descriptor. See `fs-verity descriptor`_. > > +- ``FS_VERITY_METADATA_TYPE_SIGNATURE`` reads the signature which was > + passed to FS_IOC_ENABLE_VERITY, if any. See `Built-in signature > + verification`_. > + > The semantics are similar to those of ``pread()``. ``offset`` > specifies the offset in bytes into the metadata item to read from, and > ``length`` specifies the maximum number of bytes to read from the > @@ -279,7 +284,9 @@ FS_IOC_READ_VERITY_METADATA can fail with the following errors: > - ``EINTR``: the ioctl was interrupted before any data was read > - ``EINVAL``: reserved fields were set, or ``offset + length`` > overflowed > -- ``ENODATA``: the file is not a verity file > +- ``ENODATA``: the file is not a verity file, or > + FS_VERITY_METADATA_TYPE_SIGNATURE was requested but the file doesn't > + have a built-in signature > - ``ENOTTY``: this type of filesystem does not implement fs-verity, or > this ioctl is not yet implemented on it > - ``EOPNOTSUPP``: the kernel was not configured with fs-verity > diff --git a/fs/verity/read_metadata.c b/fs/verity/read_metadata.c > index 2dea6dd3bb05a..7e2d0c7bdf0de 100644 > --- a/fs/verity/read_metadata.c > +++ b/fs/verity/read_metadata.c > @@ -114,6 +114,34 @@ static int fsverity_read_descriptor(struct inode *inode, > kfree(desc); > return res; > } > + > +static int fsverity_read_signature(struct inode *inode, > + void __user *buf, u64 offset, int length) > +{ > + struct fsverity_descriptor *desc; > + size_t desc_size; > + int res; > + > + res = fsverity_get_descriptor(inode, &desc, &desc_size); > + if (res) > + return res; > + > + if (desc->sig_size == 0) { > + res = -ENODATA; > + goto out; > + } > + > + /* > + * Include only the signature. Note that fsverity_get_descriptor() > + * already verified that sig_size is in-bounds. > + */ > + res = fsverity_read_buffer(buf, offset, length, desc->signature, > + le32_to_cpu(desc->sig_size)); > +out: > + kfree(desc); > + return res; > +} > + > /** > * fsverity_ioctl_read_metadata() - read verity metadata from a file > * @filp: file to read the metadata from > @@ -158,6 +186,8 @@ int fsverity_ioctl_read_metadata(struct file *filp, const void __user *uarg) > length); > case FS_VERITY_METADATA_TYPE_DESCRIPTOR: > return fsverity_read_descriptor(inode, buf, arg.offset, length); > + case FS_VERITY_METADATA_TYPE_SIGNATURE: > + return fsverity_read_signature(inode, buf, arg.offset, length); > default: > return -EINVAL; > } > diff --git a/include/uapi/linux/fsverity.h b/include/uapi/linux/fsverity.h > index 41abc283dbccb..15384e22e331e 100644 > --- a/include/uapi/linux/fsverity.h > +++ b/include/uapi/linux/fsverity.h > @@ -85,6 +85,7 @@ struct fsverity_formatted_digest { > > #define FS_VERITY_METADATA_TYPE_MERKLE_TREE 1 > #define FS_VERITY_METADATA_TYPE_DESCRIPTOR 2 > +#define FS_VERITY_METADATA_TYPE_SIGNATURE 3 > > struct fsverity_read_metadata_arg { > __u64 metadata_type; > -- > 2.30.0
diff --git a/Documentation/filesystems/fsverity.rst b/Documentation/filesystems/fsverity.rst index 6dc5772037ef9..1d831e3cbcb33 100644 --- a/Documentation/filesystems/fsverity.rst +++ b/Documentation/filesystems/fsverity.rst @@ -236,6 +236,7 @@ This ioctl takes in a pointer to the following structure:: #define FS_VERITY_METADATA_TYPE_MERKLE_TREE 1 #define FS_VERITY_METADATA_TYPE_DESCRIPTOR 2 + #define FS_VERITY_METADATA_TYPE_SIGNATURE 3 struct fsverity_read_metadata_arg { __u64 metadata_type; @@ -256,6 +257,10 @@ This ioctl takes in a pointer to the following structure:: - ``FS_VERITY_METADATA_TYPE_DESCRIPTOR`` reads the fs-verity descriptor. See `fs-verity descriptor`_. +- ``FS_VERITY_METADATA_TYPE_SIGNATURE`` reads the signature which was + passed to FS_IOC_ENABLE_VERITY, if any. See `Built-in signature + verification`_. + The semantics are similar to those of ``pread()``. ``offset`` specifies the offset in bytes into the metadata item to read from, and ``length`` specifies the maximum number of bytes to read from the @@ -279,7 +284,9 @@ FS_IOC_READ_VERITY_METADATA can fail with the following errors: - ``EINTR``: the ioctl was interrupted before any data was read - ``EINVAL``: reserved fields were set, or ``offset + length`` overflowed -- ``ENODATA``: the file is not a verity file +- ``ENODATA``: the file is not a verity file, or + FS_VERITY_METADATA_TYPE_SIGNATURE was requested but the file doesn't + have a built-in signature - ``ENOTTY``: this type of filesystem does not implement fs-verity, or this ioctl is not yet implemented on it - ``EOPNOTSUPP``: the kernel was not configured with fs-verity diff --git a/fs/verity/read_metadata.c b/fs/verity/read_metadata.c index 2dea6dd3bb05a..7e2d0c7bdf0de 100644 --- a/fs/verity/read_metadata.c +++ b/fs/verity/read_metadata.c @@ -114,6 +114,34 @@ static int fsverity_read_descriptor(struct inode *inode, kfree(desc); return res; } + +static int fsverity_read_signature(struct inode *inode, + void __user *buf, u64 offset, int length) +{ + struct fsverity_descriptor *desc; + size_t desc_size; + int res; + + res = fsverity_get_descriptor(inode, &desc, &desc_size); + if (res) + return res; + + if (desc->sig_size == 0) { + res = -ENODATA; + goto out; + } + + /* + * Include only the signature. Note that fsverity_get_descriptor() + * already verified that sig_size is in-bounds. + */ + res = fsverity_read_buffer(buf, offset, length, desc->signature, + le32_to_cpu(desc->sig_size)); +out: + kfree(desc); + return res; +} + /** * fsverity_ioctl_read_metadata() - read verity metadata from a file * @filp: file to read the metadata from @@ -158,6 +186,8 @@ int fsverity_ioctl_read_metadata(struct file *filp, const void __user *uarg) length); case FS_VERITY_METADATA_TYPE_DESCRIPTOR: return fsverity_read_descriptor(inode, buf, arg.offset, length); + case FS_VERITY_METADATA_TYPE_SIGNATURE: + return fsverity_read_signature(inode, buf, arg.offset, length); default: return -EINVAL; } diff --git a/include/uapi/linux/fsverity.h b/include/uapi/linux/fsverity.h index 41abc283dbccb..15384e22e331e 100644 --- a/include/uapi/linux/fsverity.h +++ b/include/uapi/linux/fsverity.h @@ -85,6 +85,7 @@ struct fsverity_formatted_digest { #define FS_VERITY_METADATA_TYPE_MERKLE_TREE 1 #define FS_VERITY_METADATA_TYPE_DESCRIPTOR 2 +#define FS_VERITY_METADATA_TYPE_SIGNATURE 3 struct fsverity_read_metadata_arg { __u64 metadata_type;